A 35-Kv Polyethylene-Insulated Cable Installation

The presently achieved and the forecasted growth in the utilization of electric power indicates higher transmission and distribution voltages. Operating voltages for bulk transmission as high as 500 kv are of interest. Distribution voltages have increased and will move further up into the range which has been used in the past for transmission. It is forecast that 69 kv surely will be, and that even 138 kv may be, in the distribution range. This situation dictates a new look at methods of distributing power, particularly by cables, since it is implied that more cables will be needed, particularly for aerial and direct burial use. Difficulties with rights-of-way and space requirements appear to require this. Impregnated-paper-insulated cables have been the major workhorses in the past and will continue to bear a large share of the burden in the solid and the various pressurized forms. However, there is no denying the advantages of a solid dielectric capable of operating in its service environments without recourse to an impervious sheath and/or pressure. Simplicity of design, installation, and operation is needed; and freedom from migration, void formation, and internal ionization phenomena is of paramount importance. Polyethylene possesses many of the properties desired for higb-voltage operation, and its use in the higher voltages is expanding. At present, 15-kv polyethylene cables are common and have a fine performance record.